| The industrial revolution has increased the use of fossil fuels.With the gas exchange between the ocean and the atmosphere,the pH value of the sea surface has decreased by about 0.1 unit.This phenomenon of ocean acidification has brought a series of impacts on marine organisms.At present,studies have shown that the decrease of pH value in seawater caused by ocean acidification has a significant impact on the survival,growth and metabolism,antioxidant stress,immune defense and other aspects of crustaceans.Marsupenaeus japonicus,as a representative of marine crustaceans,is also an important aquaculture shrimp of great research value in China.In this study,the effects of ocean acidification on the behavior of Penaeus japonicus were studied by simulating the environment of ocean acidification in laboratory.On the one hand,a variety of pH gradients were set up to explore the influence of different pH changes caused by acidified seawater on the growth parameters,sediment potential level and swimming behavior of Penaeus japonicus through data analysis and artificial intelligence technology;on the other hand,the genetic parameters of body length,abdomen length,body mass and low pH tolerance were evaluated to provide reference and suggestions for selection methods and breeding objectives and comprehensive selection index.The main results are summarized as follows:1.Effect of ocean acidification on feeding of Penaeus japonicusAcidified seawater significantly affected the feeding rate of Penaeus japonicus:the feeding rate of Penaeus japonicus in pH=7.7 seawater was 22.82%lower than that in the control group;the feeding rate of Penaeus japonicus in pH=7.3 seawater was 54.74%lower than that in the control group.At the same time,acidification of seawater also had a significant impact on the growth of Penaeus japonicus:with the increase of seawater acidification degree,the daily growth rate of body weight of Penaeus japonicus decreased significantly;the specific growth rate and feed conversion rate of Penaeus japonicus in pH=7.7 seawater were 44.19%and 29.39%lower than those in the control group;the specific growth rate and feed conversion rate of Penaeus japonicus in pH=7.3 seawater were 44.19%and 29.39%lower than those in the control group,respectively 80.94%and 57.88%respectively.The correlation coefficient between feeding rate and specific growth rate of Penaeus japonicus in acidified seawater was lower than 0.5,showing a low degree correlation.After 7 days,Penaeus japonicus can not adapt to acidified seawater,which will cause permanent damage.2.The effect of ocean acidification on the behavior of Penaeus japonicusIn general seawater(pH=8.1),the rate of sand potential of Penaeus japonicus in a day has periodic changes,and there is a rhythm of sand potential with the light intensity.6:The potential sand rate of 00-18:00 is higher than 90%,and 20:00-4:00 is lower,and 20:00 is the lowest.After five days of adaptation,the potential sand rate of prawn in the sea water with pH=7.7,7.3,6.5,5.7 and 4.9 reached 100%in the daytime,which was in line with the potential sand rhythm.However,in low pH sea water(pH=6.5,5.7,4.9),the rate of sand potential at night of Penaeus japonicus is still high,which does not conform to the rhythm of sand potential.It cannot adapt within 7 days,and will cause permanent damage.Under the natural seawater with pH=8.1,the potential sand rate of Penaeus japonicus was significantly correlated with light intensity,with a correlation coefficient of 0.9523;in the seawater with pH=7.7 and 7.3,the potential sand rate was highly correlated with light intensity,with a correlation coefficient of 0.9198 and 0.8578;in the seawater with pH=6.5,5.7 and 4.9,the potential sand rate was only moderately correlated with light intensity,with a correlation number of 0.7473,0.7351 and 0.5279,respectively.The decrease of seawater pH weakens the correlation between the rate of sand potential and light intensity,and destroys the rhythm of sand potential.3.Effect of ocean acidification on swimming behavior of Penaeus japonicusAcidified seawater can significantly reduce the movement time of Penaeus japonicus.In the natural seawater,Penaeus japonicus is in the movement state 50.46%time per hour,only 38.37%in the seawater with pH=7.7,and only 30.96%in the seawater with pH=7.3.However,acidified seawater has no significant effect on the swimming speed of Penaeus japonicus.In pH=7.7 and 7.3 seawater,the exercise time of female Penaeus japonicus was lower than that of male,with significant difference;the exercise time of 5.9cm and 7.5cm Penaeus japonicus in pH=7.7 and 7.3 seawater was significantly different,and the correlation coefficient between body length and exercise time was 0.5034,showing a moderate correlation(0.5≤r<0.8).Female and small Penaeus japonicus were more vulnerable to the negative impact of seawater acidification.4.Evaluation of genetic parameters of low pH tolerance and growth traits of Penaeus japonicusBased on the whole sib family constructed in July 2018,the genetic parameters of body length,abdomen length,body weight and low pH tolerance of Penaeus japonicus at 45 and 90 days old were obtained by hybrid linear model and constrained maximum likelihood method,respectively.The results showed that the heritability of low pH tolerance was 0.079±0.086 and 0.115±0 in two growth stages 110,which belongs to the middle and low level of heritability,and the ability of tolerance to pH is quite different among families.The correlation coefficient between growth traits and low pH tolerance phenotype is-0.0323～0.0531,and the correlation coefficient between growth traits and genetic is-0.0432～0.0652,indicating that the correlation between growth traits and pH stress tolerance is not significant,and it is difficult to improve the pH tolerance of population through single trait selection. |
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